High-performance low-carbon concrete composite admixture and preparation method thereof

Abstract

The invention relates to the technical field of building construction materials, in particular to a high-performance low-carbon concrete composite admixture and a preparation method thereof. The invention relates to a high-performance low-carbon concrete composite admixture, which is prepared from the following preparation raw materials in parts by mass: 150 to 200 parts of Portland cement, 200 to 250 parts of blast furnace slag, 400 to 450 parts of fly ash, 100 to 120 parts of active wollastonite powder, 20 to 25 parts of modified fibers, 6 to 8 parts of additives, 6 to 8 parts of high-efficiency water reducing agents and 200 to 250 parts of water. The high-performance low-carbon concrete composite admixture provided by the invention has the advantages of being simple to prepare, low in cost, green, environment-friendly, high in strength, good in crack resistance, high in durability and the like, can greatly reduce carbon emission, and is suitable for large-scale popularization and application.

Description

Technical Field

[0001] The present application relates to the technical field of building construction materials, and in particular to a high-performance low-carbon concrete composite admixture and a preparation method thereof. Background Art

[0002] The construction industry accounts for more than 40% of global carbon emissions. As the most widely used building material, concrete accounts for 6-10% of global carbon emissions. In the context of countries around the world actively "reducing carbon emissions", the development and utilization of low-carbon concrete has very important practical significance. Cement is the main source of carbon emissions from concrete. Every ton of Portland cement clinker produced emits about 830kg of CO2.

[0003] As global awareness of environmental protection grows, low-carbon building materials are gradually becoming a development trend in the construction industry. Traditional concrete has been criticized for the large amount of carbon dioxide emissions generated during its manufacturing process, which has prompted researchers to seek alternative raw materials and new preparation processes to reduce its carbon footprint. At present, there have been some reports on the use of industrial waste (such as fly ash, slag, etc.) to replace cement components, but there are generally problems such as reduced strength and insufficient durability, which limits its large-scale application.

[0004] Therefore, how to reduce carbon emissions while reducing costs and improving the mechanical properties, crack resistance and durability of concrete has become an urgent problem to be solved. Summary of the invention

[0005] The purpose of this application is to provide a high-performance low-carbon concrete composite admixture and a preparation method thereof in response to the deficiencies of current technology. The high-performance low-carbon concrete composite admixture prepared in this application has the advantages of simple preparation, low cost, and green environmental protection. It also has high early and long-term strength, crack resistance and durability, greatly reduces carbon emissions, and is suitable for large-scale promotion and application.

[0006] In the first aspect, the present application provides a high-performance low-carbon concrete composite admixture, adopting the following technical scheme: a high-performance low-carbon concrete composite admixture, calculated by weight, comprising the following preparation raw materials: 150-200 parts of silicate cement, 200-250 parts of blast furnace slag, 400-450 parts of fly ash, 100-120 parts of activated wollastonite powder, 20-25 parts of modified fiber, 6-8 parts of admixture, 6-8 parts of high-efficiency water reducer, and 200-250 parts of water.

[0007] By adopting the above technical solutions, Portland cement: as the main cementing material of concrete, it provides the necessary strength and stability. Blast furnace slag and fly ash: as mineral admixtures, these two materials can not only replace part of Portland cement to reduce carbon emissions, but also improve the pore structure of concrete and improve its durability. Active wollastonite powder: further improve the strength and durability of concrete. Modified fiber: the compatibility of fiber and concrete matrix is ​​enhanced through modification, and the crack resistance and durability of concrete are improved. At the same time, the use of this fiber also helps to utilize waste. Admixtures and high-efficiency water reducers: these additives can improve the workability of concrete, increase early strength, and reduce cement dosage and carbon emissions. Phenolic and alcohol substances in admixtures can react with active ingredients in fly ash to further improve the strength and durability of concrete. Water: as a solvent and reaction medium for concrete mixture. Mineral admixtures (blast furnace slag and fly ash) interact with Portland cement to improve the overall performance of concrete and reduce carbon emissions. The modified fiber works together with mineral admixtures and Portland cement to improve the crack resistance and durability of concrete. The admixtures and high-efficiency water reducers interact with mineral admixtures and Portland cement to improve the workability and early strength of concrete, while reducing cement usage and carbon emissions. In summary, the synergistic effect of these components in concrete not only improves the performance of concrete, but also achieves a dual improvement in environmental protection and economic benefits.

[0008] Preferably, the method for preparing the modified fiber comprises the following steps: S21. According to the mass fraction, 50 parts of chopped glass fibers are placed in 200 parts of a hydrochloric acid solution with a concentration of 80-100 g / L, heated to 50-55° C. and immersed for 3-4 hours. After filtering and washing with water, the mixture is placed in a sodium hydroxide solution with a concentration of 70 g / L and immersed for 60 minutes. The mixture is then filtered, washed with water and dried to obtain pretreated chopped glass fibers. S22, dispersing 100 parts of the pretreated chopped glass fibers in 300 parts of a solution consisting of 100 parts of ethanol and 200 parts of water, and then adding 3 parts of a silane coupling agent and 40 parts of silicon crystal waste powder, stirring and dispersing, and removing water to obtain chopped glass fibers loaded with silicon crystal waste powder; S23. According to the mass fraction, the chopped glass fibers loaded with silicon crystal waste powder are calcined at 900-1000° C. for 2-3 hours under nitrogen protection to obtain modified fibers.

[0009] By adopting the above technical scheme, when preparing the modified fiber, the surface area of ​​the chopped glass fiber particles is first treated with acid and alkali solution so that the chopped glass fiber can stably load the silicon crystal waste powder; in addition, the connection between the two is further strengthened by adding a silane coupling agent to finally prepare a stable modified fiber. The modified fiber significantly improves the strength and durability of low-carbon concrete. It is prepared with chopped glass fiber and silicon crystal waste as raw materials to achieve waste utilization; when preparing the modified fiber, the silicon crystal waste powder is appropriately loaded on the pretreated chopped glass fiber, and the composite is activated by high-temperature calcination to obtain a modified fiber with excellent compatibility with the low-carbon concrete system, which ultimately significantly improves the strength, crack resistance and durability of the low-carbon concrete.

[0010] Preferably, the silane coupling agent is one of γ-glycidyloxypropyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane; the chopped glass fiber has a length of 4-6 mm and a diameter of 13-16 μm; and the particle size of the silicon crystal waste powder is 20-30 μm.

[0011] Preferably, the high-efficiency water reducer is composed of a modified polycarboxylic acid water reducer and an aliphatic high-efficiency water reducer in a mass ratio of 3:2.

[0012] By adopting the above technical scheme, the modified polycarboxylate water reducer improves the pore structure of concrete through its steric hindrance effect and dispersibility. Improve the compressive strength and crack resistance of concrete. Work together with components such as silicate cement, blast furnace slag and fly ash to improve the workability and early and long-term strength development of concrete. Reduce cement dosage, reduce carbon emissions, and improve economic and environmental benefits. The use of aliphatic high-efficiency water reducer in combination with modified polycarboxylate water reducer can further improve the workability of concrete. Help improve the fluidity and stability of concrete. Help improve the early strength of concrete. The combined use of the two water reducers can give full play to their respective advantages and complement each other. The steric hindrance effect and dispersibility of the modified polycarboxylate water reducer can be combined with the water-reducing effect of the aliphatic high-efficiency water reducer to further improve the workability and strength of concrete. By adjusting the ratio of the two water reducers, the fine regulation of concrete performance can be achieved. In summary, the synergistic effect of high-efficiency water reducers can effectively improve the comprehensive properties of concrete, including workability, strength, crack resistance and durability. At the same time, this combination also has good environmental and economic benefits by reducing cement consumption and lowering carbon emissions.

[0013] Preferably, the preparation method of the modified polycarboxylate water-reducing agent comprises the following steps: S51, adding 18 mol of acrylic acid and 1 mol of vinyltriethoxysilane to 6 kg of water, stirring evenly, to obtain a mixed solution A; S52. Add 0.5 mol of vitamin C and 0.9 mol of 3-mercaptopropionic acid to 3 kg of water, stir evenly, and obtain a mixed solution B. S53. Add 0.8 mol of bisallyl alcohol-terminated polyoxyethylene ether and 6 mol of oleyl alcohol polyoxyethylene (10) ether to 24 kg of water and stir, then add 1.2 mol of hydrogen peroxide, stir and heat to 49-53°C, then dropwise add the mixed solution A and the mixed solution B at the same time. After the addition is completed for 3 hours, continue stirring and react for 4-5 hours, then add an aqueous solution of NaOH to adjust the pH value to 6.5-7.0, and obtain a modified polycarboxylic acid water reducer.

[0014] By adopting the above technical scheme, the prepared modified polycarboxylate water-reducing agent can effectively disperse cement particles and reduce flocculation in cement paste through the steric hindrance effect in its molecular structure, thereby improving the workability of concrete, that is, fluidity. By improving the pore structure of concrete, the modified polycarboxylate water-reducing agent helps to improve the compressive strength and crack resistance of concrete. The improvement of the pore structure means that the interior of the concrete is more uniform and dense, reducing the generation and development of microcracks. The modified polycarboxylate water-reducing agent can promote the early strength development of concrete and also help to improve the long-term strength. This is because the water-reducing agent can accelerate the speed of cement hydration reaction, thereby improving the strength of concrete. By improving the workability and strength of concrete, the modified polycarboxylate water-reducing agent helps to reduce the amount of cement. This not only reduces costs, but also reduces carbon emissions in the cement production process. The modified polycarboxylate water-reducing agent works together with aliphatic high-efficiency water-reducing agents and other components in concrete (such as silicate cement, blast furnace slag and fly ash, etc.) to further improve the performance of concrete. For example, when used in conjunction with admixtures and high-efficiency water reducers, the doping effect of fly ash and blast furnace slag can be enhanced, and the early strength of concrete can be improved. By reducing cement dosage and improving concrete performance, modified polycarboxylate water reducers help achieve both economic and environmental benefits. This not only reduces production costs, but also reduces environmental impact. In summary, modified polycarboxylate water reducers play a vital role in the concrete preparation process, not only improving the performance of concrete, but also helping to achieve green environmental protection and sustainable development.

[0015] Preferably, the admixture comprises the following raw materials, measured by weight: 100 parts of hydroxyethyl acrylate, 0.2 parts of dicumyl peroxide, 19 parts of methoxypolyoxyethylene ether, 6 parts of methyldiethanolamine, 1 part of hexadecyltrimethylammonium hydroxide, 5 parts of dopamine, 110 parts of acetone, and 100 parts of water. The preparation method of the admixture is as follows: according to the weight parts, hydroxyethyl acrylate, dicumyl peroxide, methoxypolyoxyethylene ether, methyldiethanolamine, hexadecyltrimethylammonium hydroxide, dopamine, acetone and water are mixed, the temperature is raised to 45°C, and the reaction is stirred for 50 minutes to obtain the admixture.

[0016] By adopting the above technical scheme, the phenolic substances and alcoholic substances contained in the admixture can coordinate with the active ingredients (such as iron ions and aluminum ions) in fly ash and blast furnace slag, thereby destroying the glassy structure of the surface layer of fly ash and promoting the release of active SiO2 and active Al2O3. This helps to improve the reactivity of fly ash and blast furnace slag, so that they participate in the hydration reaction faster, thereby improving the early strength of concrete. The admixture can accelerate the release of active ingredients in fly ash by dissolving the surface structure of fly ash particles, thereby partially replacing the role of silicate cement. This not only reduces the amount of cement used, but also reduces the carbon emissions in the concrete preparation process. Various ingredients in the admixture (such as hydroxyethyl acrylate, methoxy polyoxyethylene ether, etc.) help to improve the fluidity and plasticity of concrete, making concrete easier to mix, transport and form. This is of great significance for the large-scale promotion and application of high-performance low-carbon concrete. Components such as dopamine in the admixture can form stable chemical bonds with other components in concrete, enhance the microstructural stability of concrete, thereby improving its crack resistance and long-term durability. Phenolic substances combined with high-efficiency water reducers greatly improve the dispersibility of cement particles due to steric hindrance. This helps to reduce the agglomeration of cement particles and make them more evenly distributed in concrete, thereby improving the overall performance of concrete. High-efficiency water reducers can significantly reduce the water-cement ratio of concrete, while admixtures further optimize the pore structure of concrete, so that the amount of water can be further reduced while maintaining the same fluidity. This helps to improve the density and strength of concrete. The combined effect of admixtures and high-efficiency water reducers not only improves the early and long-term strength of concrete, but also improves its crack resistance and durability. Admixtures play an important role in the preparation of high-performance low-carbon concrete and have a good synergistic effect with high-efficiency water reducers. These effects jointly promote the improvement of concrete performance and achieve the dual goals of economic and environmental benefits.

[0017] Preferably, the particle size of the activated wollastonite powder is 325 mesh; and the fly ash is grade II fly ash.

[0018] Preferably, the silicate cement is P·O42.5 cement, the particle size of the blast furnace slag ranges from 0.04 to 0.06 mm, and its chemical composition includes: 35.6% CaO, 33.2% SiO2, 12.7% Al2O3, 9.2% MgO, 2.5% TiO2, 1.3% Fe2O3 and other substances.

[0019] In a second aspect, the present application provides a method for preparing a high-performance low-carbon concrete composite admixture, using the following technical solution: As a general technical concept, the present application also provides a method for preparing the above-mentioned high-performance low-carbon concrete composite admixture, comprising the following steps: S101. Mix silicate cement, blast furnace slag, fly ash, activated wollastonite powder, modified fiber, admixture and high-efficiency water reducing agent evenly according to their weight proportions, and then add water and stir for 2-3 minutes to obtain a high-performance low-carbon concrete composite admixture slurry; S102, mold, shape and demould the high-performance low-carbon concrete composite admixture slurry, and continue to cure to obtain the high-performance low-carbon concrete composite admixture.

[0020] In summary, the beneficial technical effects of this application are: 1. Low-carbon and environmentally friendly: By using blast furnace slag and fly ash to replace part of the silicate cement, the amount of cement used and carbon emissions are reduced, achieving the goal of low-carbon and environmentally friendly. At the same time, this substitution not only reduces production costs, but also reduces dependence on natural resources.

[0021] 2. Improve strength and durability: The use of modified fibers significantly improves the strength and durability of concrete. Modified fibers can effectively enhance the structural properties of concrete.

[0022] 3. Improve pore structure and crack resistance: Modified polycarboxylate water reducer improves the pore structure of concrete, enhances compressive strength and crack resistance through its steric hindrance effect and dispersion performance. At the same time, the use of this water reducer also promotes the early and long-term strength development of concrete.

[0023] 4. Improve workability and reduce cement usage: The use of admixtures and high-efficiency water reducers improves the doping effect of fly ash and blast furnace slag, further reducing the amount of cement. At the same time, these additives can also improve the workability of concrete and reduce energy consumption and costs during the preparation process.

[0024] 5. Economic and environmental benefits: Through the comprehensive application of the above technical measures, this application not only improves the performance of concrete, but also achieves a dual improvement in economic and environmental benefits, which is specifically reflected in reducing production costs, reducing carbon emissions, and improving resource utilization efficiency. DETAILED DESCRIPTION

[0025] The embodiments of the present application will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0026] In the following embodiments, preparation examples and comparative preparation examples, 1 part represents 1 kg, the fly ash is Class II fly ash, the particle size of the activated wollastonite powder is 325 mesh; the silicate cement is P·O42.5 cement, the particle size range of blast furnace slag is 0.04-0.06 mm, and its chemical composition includes: 35.6% CaO, 33.2% SiO2, 12.7% Al2O3, 9.2% MgO, 2.5% TiO2, 1.3% Fe2O3 and other substances.

[0027] Preparation Example 1 Preparation of modified fiber The preparation method of the modified fiber comprises the following steps: S21. According to the mass fraction, 50 parts of chopped glass fibers with a length of 4-6 mm and a diameter of 13-16 μm are placed in 200 parts of a hydrochloric acid solution with a concentration of 90 g / L, heated to 53° C. and immersed for 3.4 hours. After filtering and washing with water, the mixture is placed in a sodium hydroxide solution with a concentration of 70 g / L and immersed for 60 minutes. Then, the mixture is filtered, washed with water and dried to obtain pretreated chopped glass fibers. S22, dispersing 100 parts of the pretreated chopped glass fibers in 300 parts of a solution consisting of 100 parts of ethanol and 200 parts of water, according to the mass fraction, and then adding 3 parts of γ-methacryloxypropyltrimethoxysilane and 40 parts of silicon crystal waste powder with a particle size of 20-30 μm, stirring and dispersing, and removing water to obtain chopped glass fibers loaded with silicon crystal waste powder; S23. According to the mass fraction, the chopped glass fibers loaded with silicon crystal waste powder are calcined at 960° C. for 2.5 h under nitrogen protection to obtain modified fibers.

[0028] Preparation Example 2 Preparation of modified polycarboxylate water reducer The preparation method of the modified polycarboxylate water-reducing agent comprises the following steps: S51, adding 18 mol of acrylic acid and 1 mol of vinyltriethoxysilane to 6 kg of water, stirring evenly, to obtain a mixed solution A; S52, adding 0.5 mol of vitamin C and 0.9 mol of 3-mercaptopropionic acid to 3 kg of water, stirring evenly, to obtain a mixed solution B; S53. Add 0.8 mol of bisallyl alcohol-terminated polyoxyethylene ether and 6 mol of oleyl alcohol polyoxyethylene (10) ether to 24 kg of water and stir, then add 1.2 mol of hydrogen peroxide, stir and heat to 53°C, then dropwise add mixed solution A and mixed solution B at the same time. After the addition is completed within 3 hours, continue stirring and reacting for 4.5 hours, then add NaOH aqueous solution to adjust the pH value to 6.6, and obtain a modified polycarboxylic acid water reducer.

[0029] Preparation Example 3 Preparation of admixture The admixture comprises the following raw materials, calculated by weight: 100 parts of hydroxyethyl acrylate, 0.2 parts of dicumyl peroxide, 19 parts of methoxypolyoxyethylene ether, 6 parts of methyldiethanolamine, 1 part of hexadecyltrimethylammonium hydroxide, 5 parts of dopamine, 110 parts of acetone, and 100 parts of water. The preparation method of the admixture is as follows: according to the weight parts, hydroxyethyl acrylate, dicumyl peroxide, methoxypolyoxyethylene ether, methyldiethanolamine, hexadecyltrimethylammonium hydroxide, dopamine, acetone and water are mixed, the mixture is heated to 45°C, and the mixture is stirred for reaction for 50 minutes to obtain the admixture.

[0030] Example 1 A high-performance low-carbon concrete composite admixture, comprising the following raw materials by weight: 150 parts of silicate cement, 200 parts of blast furnace slag, 400 parts of fly ash, 100 parts of active wollastonite powder, 20 parts of modified fiber, 6 parts of admixture, 6 parts of high-efficiency water reducer, and 200 parts of water, wherein the high-efficiency water reducer is composed of a modified polycarboxylate water reducer and an aliphatic high-efficiency water reducer in a weight ratio of 3:2; The method for preparing the high-performance low-carbon concrete composite admixture comprises the following steps: S101. Mix silicate cement, blast furnace slag, fly ash, activated wollastonite powder, modified fiber, admixture and high-efficiency water reducing agent evenly according to their weight proportions, and then add water and stir for 2 minutes to obtain a high-performance low-carbon concrete composite admixture slurry; S102, mold, shape and demould the high-performance low-carbon concrete composite admixture slurry, and continue to cure to obtain the high-performance low-carbon concrete composite admixture.

[0031] Example 2 A high-performance low-carbon concrete composite admixture, comprising the following raw materials by weight: 200 parts of silicate cement, 250 parts of blast furnace slag, 450 parts of fly ash, 120 parts of active wollastonite powder, 25 parts of modified fiber, 8 parts of admixture, 8 parts of high-efficiency water reducer, and 250 parts of water, wherein the high-efficiency water reducer is composed of a modified polycarboxylate water reducer and an aliphatic high-efficiency water reducer in a weight ratio of 3:2; The method for preparing the high-performance low-carbon concrete composite admixture comprises the following steps: S101. Mix silicate cement, blast furnace slag, fly ash, activated wollastonite powder, modified fiber, admixture and high-efficiency water reducing agent evenly according to their weight proportions, and then add water and stir for 3 minutes to obtain a high-performance low-carbon concrete composite admixture slurry; S102, mold, shape and demould the high-performance low-carbon concrete composite admixture slurry, and continue to cure to obtain the high-performance low-carbon concrete composite admixture.

[0032] Example 3 A high-performance low-carbon concrete composite admixture, comprising the following raw materials by weight: 180 parts of silicate cement, 220 parts of blast furnace slag, 430 parts of fly ash, 110 parts of active wollastonite powder, 23 parts of modified fiber, 7 parts of admixture, 7 parts of high-efficiency water reducer, and 230 parts of water, wherein the high-efficiency water reducer is composed of a modified polycarboxylate water reducer and an aliphatic high-efficiency water reducer in a weight ratio of 3:2; The method for preparing the high-performance low-carbon concrete composite admixture comprises the following steps: S101. Mix silicate cement, blast furnace slag, fly ash, activated wollastonite powder, modified fiber, admixture and high-efficiency water reducing agent evenly according to their weight proportions, and then add water and stir for 2.3 minutes to obtain a high-performance low-carbon concrete composite admixture slurry; S102, mold, shape and demould the high-performance low-carbon concrete composite admixture slurry, and continue to cure to obtain the high-performance low-carbon concrete composite admixture.

[0033] Comparative Example 1 The same as Example 3, except that an equal amount of chopped glass fibers with a length of 4-6 mm and a diameter of 13-16 μm are used instead of the modified fibers.

[0034] Comparative Example 2 The same as Example 3, except that the high-efficiency water reducer is a modified polycarboxylic acid water reducer.

[0035] Comparative Example 3 The same as Example 3, except that the high-efficiency water reducer is an aliphatic high-efficiency water reducer.

[0036] Comparative Example 4 The same as Example 3, except that the admixture is 0 parts and the high-efficiency water reducing agent is 8 parts.

[0037] Comparative Example 5 The same as Example 3, except that the admixture is 8 parts and the high-efficiency water reducing agent is 0 parts.

[0038] Performance Testing The high-performance low-carbon concrete composite admixtures prepared in Examples 1 to 3 and Comparative Examples 1 to 5 were made into test pieces. The test piece size was a cube with a side length of 150 mm. The surface was sealed with a polyethylene film and cured at room temperature for 24 hours before demolding. The specimen was moved to a standard curing box and cured to the corresponding age. The following tests were performed. The test results are shown in Table 1.

[0039] Compressive strength: Tested in accordance with the relevant provisions of GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Ordinary Concrete"; Durability test: refer to GB / T 50082-2009 "Standard for test methods of long-term performance and durability of ordinary concrete" to conduct durability test on the product; Shrinkage rate: According to the shrinkage test in GBJ82-85 "Test method for long-term performance and durability of ordinary concrete", the 28d shrinkage value is tested. In addition, the crack condition of the crack surface of the test block is checked.

[0040] Table 1 Performance test project 7d compressive strength / MPa 28d compressive strength / MPa 28d shrinkage / % <![CDATA[Number of cracks / root / m 2 > Example 1 82.3 99.4 0.019 none Example 2 83.6 101.3 0.015 none Example 3 85.6 104.8 0.012 none Comparative Example 1 72.4 83.2 0.031 2 Comparative Example 2 81.2 98.5 0.23 none Comparative Example 3 79.3 94.3 0.26 1 Comparative Example 4 76.7 88.7 0.27 5 Comparative Example 5 78.2 91.2 0.28 3 Analyzing the data in Table 1, we can see that: 1) The high-performance low-carbon concrete composite admixtures prepared in Examples 1 to 3 have high early and long-term strength, crack resistance and durability, significantly reduce carbon emissions, and are suitable for large-scale promotion and application.

[0041] 2) The comparative analysis of the performance of the high-performance low-carbon concrete composite admixtures prepared in combination with Example 3 and Comparative Example 1 shows that the modified fiber prepared in the present application significantly improves the strength and durability of the low-carbon concrete, and is prepared using chopped glass fiber and silicon crystal waste as raw materials to achieve waste utilization; when preparing the modified fiber, an appropriate amount of silicon crystal waste powder is loaded on the modified fiber, and the composite is activated by high-temperature calcination to obtain a modified fiber with excellent compatibility with the low-carbon concrete system, which ultimately significantly improves the strength, crack resistance and durability of the low-carbon concrete.

[0042] 3) The performance comparison analysis of the high-performance low-carbon concrete composite admixtures prepared in combination with Example 3 and Comparative Examples 2-3 shows that the high-efficiency water reducer is composed of a modified polycarboxylate water reducer and an aliphatic high-efficiency water reducer in a mass ratio of 3:2, and the modified polycarboxylate water reducer improves the pore structure of the concrete through its steric hindrance effect and dispersibility. Improve the compressive strength and crack resistance of concrete. Work together with components such as silicate cement, blast furnace slag and fly ash to improve the workability and early and long-term strength development of concrete. Reduce cement consumption, reduce carbon emissions, and improve economic and environmental benefits. The use of aliphatic high-efficiency water reducers in combination with modified polycarboxylate water reducers can further improve the workability of concrete. It helps to improve the fluidity and stability of concrete. It helps to improve the early strength of concrete. The combined use of the two water reducers can give play to their respective advantages and complement each other's shortcomings. The steric hindrance effect and dispersibility of the modified polycarboxylate water reducer can be combined with the water-reducing effect of the aliphatic high-efficiency water reducer to further improve the workability and strength of concrete. In summary, the synergistic effect of high-efficiency water-reducing agents can effectively improve the comprehensive performance of concrete, including workability, strength, crack resistance and durability. At the same time, by reducing cement consumption and reducing carbon emissions, this combination also has good environmental and economic benefits.

[0043] 4) The performance comparison analysis of the high-performance low-carbon concrete composite admixture prepared in combination with Example 3 and Comparative Examples 4-5 shows that the admixture contained in this application has a good coordination effect with the high-efficiency water reducing agent, improves the doping effect of fly ash and blast furnace slag, further reduces the amount of cement used, and improves the early strength of concrete. Specifically, the surface glass of fly ash is destroyed by the water reducing agent to improve the leaching of valuable elements. The phenolic substances in the admixture can coordinate with the leached iron ions and aluminum ions with alcohol substances, dissolve the surface structure of fly ash particles, so that fly ash or blast furnace slag powder releases active SiO2 and active Al2O3 faster, thereby stimulating the activity of fly ash. Relative to alcohol substances, phenolic substances cooperate with water reducing agents, and due to the steric hindrance, the dispersibility of cement particles is greatly improved, which can effectively reduce the amount of cement used in concrete preparation and effectively reduce the carbon emissions in concrete. At the same time, the strength, crack resistance and durability of low-carbon concrete are improved.

[0044] The above embodiments are only used to explain the technical solutions of the present application rather than to limit them. Although the above embodiments provide a specific description of the present application, relevant technical personnel should understand that the specific implementation modes of the present invention can still be modified or replaced by equivalents, and any modifications and equivalent replacements that do not depart from the spirit and scope of the present application should be included in the scope of protection of the present application.

Claims

1. A high performance low carbon concrete composite admixture, characterized in that: The preparation raw materials include the following by weight: 150-200 parts of silicate cement, 200-250 parts of blast furnace slag, 400-450 parts of fly ash, 100-120 parts of active wollastonite powder, 20-25 parts of modified fiber, 6-8 parts of admixture, 6-8 parts of high-efficiency water reducing agent and 200-250 parts of water.

2. A high performance low carbon concrete composite admixture according to claim 1, characterized in that: The method for preparing the modified fiber comprises the following steps: S21. According to the mass fraction, 50 parts of chopped glass fibers are placed in 200 parts of a hydrochloric acid solution with a concentration of 80-100 g / L, heated to 50-55° C. and immersed for 3-4 hours. After filtering and washing with water, the mixture is placed in a sodium hydroxide solution with a concentration of 70 g / L and immersed for 60 minutes. The mixture is then filtered, washed with water and dried to obtain pretreated chopped glass fibers. S22, dispersing 100 parts of the pretreated chopped glass fibers in 300 parts of a solution consisting of 100 parts of ethanol and 200 parts of water, and then adding 3 parts of a silane coupling agent and 40 parts of silicon crystal waste powder, stirring and dispersing, and removing water to obtain chopped glass fibers loaded with silicon crystal waste powder; S23. According to the mass fraction, the chopped glass fibers loaded with silicon crystal waste powder are calcined at 900-1000° C. for 2-3 hours under nitrogen protection to obtain modified fibers.

3. A high performance low carbon concrete composite admixture according to claim 2, characterized in that: The silane coupling agent is one of γ-glycidyloxypropyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane; the length of the chopped glass fiber is 4-6mm and the diameter is 13-16μm; the particle size of the silicon crystal waste powder is 20-30μm.

4. A high performance low carbon concrete composite admixture according to claim 1, characterized in that: The high-efficiency water reducer is composed of a modified polycarboxylic acid water reducer and an aliphatic high-efficiency water reducer in a mass ratio of 3:

2.

5. A high performance low carbon concrete composite admixture according to claim 4, characterized in that: The preparation method of the modified polycarboxylate water-reducing agent comprises the following steps: S51, adding 18 mol of acrylic acid and 1 mol of vinyltriethoxysilane to 6 kg of water, stirring evenly, to obtain a mixed solution A; S52, adding 0.5 mol of vitamin C and 0.9 mol of 3-mercaptopropionic acid to 3 kg of water, stirring evenly, to obtain a mixed solution B; S53. Add 0.8 mol of bisallyl alcohol-terminated polyoxyethylene ether and 6 mol of oleyl alcohol polyoxyethylene (10) ether to 24 kg of water and stir, then add 1.2 mol of hydrogen peroxide, stir and heat to 49-53 ° C, then drop the mixed solution A and mixed solution B at the same time. After the addition is completed for 3 hours, continue to stir and react for 4-5 hours, then add NaOH aqueous solution to adjust the pH value to 6.5-7.0, and obtain the modified polycarboxylic acid water reducer.

6. The high performance low carbon concrete composite admixture according to claim 1, characterized in that: The admixture includes the following raw materials by weight: 100 parts of hydroxyethyl acrylate, 0.2 parts of diisopropylbenzene peroxide, 19 parts of methoxypolyoxyethylene ether, 6 parts of methyldiethanolamine, 1 part of hexadecyltrimethylammonium hydroxide, 5 parts of dopamine, 110 parts of acetone, and 100 parts of water.

7. A high performance low carbon concrete composite admixture according to claim 6, characterized in that: The preparation method of the additive is as follows: according to the mass fractions, hydroxyethyl acrylate, diisopropylbenzene peroxide, methoxypolyoxyethylene ether, methyldiethanolamine, hexadecyltrimethylammonium hydroxide, dopamine, acetone and water are mixed, the mixture is heated to 45° C., and the mixture is stirred for reaction for 50 minutes to obtain the additive.

8. The high performance low carbon concrete composite admixture according to claim 1, characterized in that: The particle size of the activated wollastonite powder is 325 meshes; the fly ash is grade II fly ash.

9. The high performance low carbon concrete composite admixture according to claim 1, characterized in that: The silicate cement is P·O42.5 cement, the particle size of the blast furnace slag is in the range of 0.04-0.06 mm, and its chemical composition includes: 35.6% CaO, 33.2% SiO2, 12.7% Al2O3, 9.2% MgO, 2.5% TiO2, 1.3% Fe2O3 and other substances.

10. A method for preparing a high-performance low-carbon concrete composite admixture according to any one of claims 1 to 9, characterized in that: The following steps are involved: S101. Mix silicate cement, blast furnace slag, fly ash, activated wollastonite powder, modified fiber, admixture and high-efficiency water reducing agent evenly according to their weight proportions, and then add water and stir for 2-3 minutes to obtain a high-performance low-carbon concrete composite admixture slurry; S102, mold, shape and demould the high-performance low-carbon concrete composite admixture slurry, and continue to cure to obtain the high-performance low-carbon concrete composite admixture.